“I can just see the Mexican president — ‘Donald Trump, take this wall down,’ ” Johnson said on Fox Business Network. “He’s going to be on the right side of history at some point if Trump is elected and if he does this wall, which is really asinine. We will take it down at some point.”

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Johnson, a former Republican governor of New Mexico, also called it impractical to build a wall along the lengthy U.S. southern border.

“I mean, we’re talking about 2,500 miles,” said Johnson. “How’s the wall going to work when it comes to Texas and Mexico when the border is the Rio Grande River?

“Are we going to build the wall on our side of the river? Their side? Oh, I see, right down the middle of the river. I mean, really, this is just crazy,” he said.

Johnson also said Trump, the Republican presidential nominee, is wrong to suggest that immigration is hurting America economically.

“Immigrants are not taking jobs that U.S. citizens want,” he said. "We should be embracing immigration.

“The reason there’s 11 million undocumented workers is because they can’t get across the border legally, and yet the jobs exist, so they’re forced to cross illegally,” Johnson added.

“And, by the way, the illegal crossings are at like a 10-year low. We should be making it as easy as possible for somebody who wants to come into this country and work to be able to get a work visa.”

Trump has repeatedly insisted that Mexico will pay to build a border wall.